/*
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package qunar.tc.bistoury.instrument.client.spring.el;

import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;


/**
 * Context about a type to convert from or to.
 *
 * @author Keith Donald
 * @author Andy Clement
 * @author Juergen Hoeller
 * @author Phillip Webb
 * @author Sam Brannen
 * @since 3.0
 */
@SuppressWarnings("serial")
class TypeDescriptor implements Serializable {

    static final Annotation[] EMPTY_ANNOTATION_ARRAY = new Annotation[0];

    private static final Map<Class<?>, TypeDescriptor> typeDescriptorCache = new HashMap<Class<?>, TypeDescriptor>();

    static {
        typeDescriptorCache.put(boolean.class, new TypeDescriptor(boolean.class));
        typeDescriptorCache.put(Boolean.class, new TypeDescriptor(Boolean.class));
        typeDescriptorCache.put(byte.class, new TypeDescriptor(byte.class));
        typeDescriptorCache.put(Byte.class, new TypeDescriptor(Byte.class));
        typeDescriptorCache.put(char.class, new TypeDescriptor(char.class));
        typeDescriptorCache.put(Character.class, new TypeDescriptor(Character.class));
        typeDescriptorCache.put(short.class, new TypeDescriptor(short.class));
        typeDescriptorCache.put(Short.class, new TypeDescriptor(Short.class));
        typeDescriptorCache.put(int.class, new TypeDescriptor(int.class));
        typeDescriptorCache.put(Integer.class, new TypeDescriptor(Integer.class));
        typeDescriptorCache.put(long.class, new TypeDescriptor(long.class));
        typeDescriptorCache.put(Long.class, new TypeDescriptor(Long.class));
        typeDescriptorCache.put(float.class, new TypeDescriptor(float.class));
        typeDescriptorCache.put(Float.class, new TypeDescriptor(Float.class));
        typeDescriptorCache.put(double.class, new TypeDescriptor(double.class));
        typeDescriptorCache.put(Double.class, new TypeDescriptor(Double.class));
        typeDescriptorCache.put(String.class, new TypeDescriptor(String.class));
    }


    private final Class<?> type;

    private final TypeDescriptor elementTypeDescriptor;

    private final TypeDescriptor mapKeyTypeDescriptor;

    private final TypeDescriptor mapValueTypeDescriptor;

    private final Annotation[] annotations;


    /**
     * Create a new type descriptor from a {@link MethodParameter}.
     * <p>Use this constructor when a source or target conversion point is a
     * constructor parameter, method parameter, or method return value.
     *
     * @param methodParameter the method parameter
     */
    public TypeDescriptor(MethodParameter methodParameter) {
        this(new ParameterDescriptor(methodParameter));
    }

    /**
     * Create a new type descriptor from a {@link Field}.
     * <p>Use this constructor when a source or target conversion point is a field.
     *
     * @param field the field
     */
    public TypeDescriptor(Field field) {
        this(new FieldDescriptor(field));
    }

    /**
     * Create a new type descriptor from a {@link Property}.
     * <p>Use this constructor when a source or target conversion point is a
     * property on a Java class.
     *
     * @param property the property
     */
    public TypeDescriptor(Property property) {
        this(new BeanPropertyDescriptor(property));
    }


    /**
     * Create a new type descriptor from the given type.
     * <p>Use this to instruct the conversion system to convert an object to a
     * specific target type, when no type location such as a method parameter or
     * field is available to provide additional conversion context.
     * <p>Generally prefer use of {@link #forObject(Object)} for constructing type
     * descriptors from source objects, as it handles the {@code null} object case.
     *
     * @param type the class
     * @return the type descriptor
     */
    public static TypeDescriptor valueOf(Class<?> type) {
        TypeDescriptor desc = typeDescriptorCache.get(type);
        return (desc != null ? desc : new TypeDescriptor(type));
    }

    /**
     * Create a new type descriptor from a {@link Collection} type.
     * <p>Useful for converting to typed Collections.
     * <p>For example, a {@code List<String>} could be converted to a
     * {@code List<EmailAddress>} by converting to a targetType built with this method.
     * The method call to construct such a {@code TypeDescriptor} would look something
     * like: {@code collection(List.class, TypeDescriptor.valueOf(EmailAddress.class));}
     *
     * @param collectionType        the collection type, which must implement {@link Collection}.
     * @param elementTypeDescriptor a descriptor for the collection's element type,
     *                              used to convert collection elements
     * @return the collection type descriptor
     */
    public static TypeDescriptor collection(Class<?> collectionType, TypeDescriptor elementTypeDescriptor) {
        if (!Collection.class.isAssignableFrom(collectionType)) {
            throw new IllegalArgumentException("collectionType must be a java.util.Collection");
        }
        return new TypeDescriptor(collectionType, elementTypeDescriptor);
    }

    /**
     * Create a new type descriptor from a {@link Map} type.
     * <p>Useful for converting to typed Maps.
     * <p>For example, a Map&lt;String, String&gt; could be converted to a Map&lt;Id, EmailAddress&gt; by converting to a targetType built with this method:
     * The method call to construct such a TypeDescriptor would look something like: map(Map.class, TypeDescriptor.valueOf(Id.class), TypeDescriptor.valueOf(EmailAddress.class));
     *
     * @param mapType             the map type, which must implement {@link Map}
     * @param keyTypeDescriptor   a descriptor for the map's key type, used to convert map keys
     * @param valueTypeDescriptor the map's value type, used to convert map values
     * @return the map type descriptor
     */
    public static TypeDescriptor map(Class<?> mapType, TypeDescriptor keyTypeDescriptor, TypeDescriptor valueTypeDescriptor) {
        if (!Map.class.isAssignableFrom(mapType)) {
            throw new IllegalArgumentException("mapType must be a java.util.Map");
        }
        return new TypeDescriptor(mapType, keyTypeDescriptor, valueTypeDescriptor);
    }

    /**
     * Create a new type descriptor as an array of the specified type.
     * <p>For example to create a {@code Map<String,String>[]} use
     * {@code TypeDescriptor.array(TypeDescriptor.map(Map.class, TypeDescriptor.value(String.class), TypeDescriptor.value(String.class)))}.
     *
     * @param elementTypeDescriptor the {@link TypeDescriptor} of the array element or {@code null}
     * @return an array {@link TypeDescriptor} or {@code null} if {@code elementTypeDescriptor} is {@code null}
     * @since 3.2.1
     */
    public static TypeDescriptor array(TypeDescriptor elementTypeDescriptor) {
        if (elementTypeDescriptor == null) {
            return null;
        }
        Class<?> type = Array.newInstance(elementTypeDescriptor.getType(), 0).getClass();
        return new TypeDescriptor(type, elementTypeDescriptor, null, null, elementTypeDescriptor.getAnnotations());
    }

    /**
     * Creates a type descriptor for a nested type declared within the method parameter.
     * <p>For example, if the methodParameter is a {@code List<String>} and the
     * nesting level is 1, the nested type descriptor will be String.class.
     * <p>If the methodParameter is a {@code List<List<String>>} and the nesting
     * level is 2, the nested type descriptor will also be a String.class.
     * <p>If the methodParameter is a {@code Map<Integer, String>} and the nesting
     * level is 1, the nested type descriptor will be String, derived from the map value.
     * <p>If the methodParameter is a {@code List<Map<Integer, String>>} and the
     * nesting level is 2, the nested type descriptor will be String, derived from the map value.
     * <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
     * For example, if the method parameter is a {@code List<?>}, the nested type
     * descriptor returned will be {@code null}.
     *
     * @param methodParameter the method parameter with a nestingLevel of 1
     * @param nestingLevel    the nesting level of the collection/array element or
     *                        map key/value declaration within the method parameter
     * @return the nested type descriptor at the specified nesting level, or null
     * if it could not be obtained
     * @throws IllegalArgumentException if the nesting level of the input
     *                                  {@link MethodParameter} argument is not 1
     * @throws IllegalArgumentException if the types up to the specified nesting
     *                                  level are not of collection, array, or map types
     */
    public static TypeDescriptor nested(MethodParameter methodParameter, int nestingLevel) {
        if (methodParameter.getNestingLevel() != 1) {
            throw new IllegalArgumentException("methodParameter nesting level must be 1: use the nestingLevel parameter to specify the desired nestingLevel for nested type traversal");
        }
        return nested(new ParameterDescriptor(methodParameter), nestingLevel);
    }

    /**
     * Creates a type descriptor for a nested type declared within the field.
     * <p>For example, if the field is a {@code List<String>} and the nesting
     * level is 1, the nested type descriptor will be {@code String.class}.
     * <p>If the field is a {@code List<List<String>>} and the nesting level is
     * 2, the nested type descriptor will also be a {@code String.class}.
     * <p>If the field is a {@code Map<Integer, String>} and the nesting level
     * is 1, the nested type descriptor will be String, derived from the map value.
     * <p>If the field is a {@code List<Map<Integer, String>>} and the nesting
     * level is 2, the nested type descriptor will be String, derived from the map value.
     * <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
     * For example, if the field is a {@code List<?>}, the nested type descriptor returned will be {@code null}.
     *
     * @param field        the field
     * @param nestingLevel the nesting level of the collection/array element or
     *                     map key/value declaration within the field
     * @return the nested type descriptor at the specified nesting level, or null
     * if it could not be obtained
     * @throws IllegalArgumentException if the types up to the specified nesting
     *                                  level are not of collection, array, or map types
     */
    public static TypeDescriptor nested(Field field, int nestingLevel) {
        return nested(new FieldDescriptor(field), nestingLevel);
    }

    /**
     * Creates a type descriptor for a nested type declared within the property.
     * <p>For example, if the property is a {@code List<String>} and the nesting
     * level is 1, the nested type descriptor will be {@code String.class}.
     * <p>If the property is a {@code List<List<String>>} and the nesting level
     * is 2, the nested type descriptor will also be a {@code String.class}.
     * <p>If the property is a {@code Map<Integer, String>} and the nesting level
     * is 1, the nested type descriptor will be String, derived from the map value.
     * <p>If the property is a {@code List<Map<Integer, String>>} and the nesting
     * level is 2, the nested type descriptor will be String, derived from the map value.
     * <p>Returns {@code null} if a nested type cannot be obtained because it was not declared.
     * For example, if the property is a {@code List<?>}, the nested type descriptor
     * returned will be {@code null}.
     *
     * @param property     the property
     * @param nestingLevel the nesting level of the collection/array element or
     *                     map key/value declaration within the property
     * @return the nested type descriptor at the specified nesting level, or
     * {@code null} if it could not be obtained
     * @throws IllegalArgumentException if the types up to the specified nesting
     *                                  level are not of collection, array, or map types
     */
    public static TypeDescriptor nested(Property property, int nestingLevel) {
        return nested(new BeanPropertyDescriptor(property), nestingLevel);
    }

    /**
     * Create a new type descriptor for an object.
     * <p>Use this factory method to introspect a source object before asking the conversion system to convert it to some another type.
     * <p>If the provided object is null, returns null, else calls {@link #valueOf(Class)} to build a TypeDescriptor from the object's class.
     *
     * @param source the source object
     * @return the type descriptor
     */
    public static TypeDescriptor forObject(Object source) {
        return (source != null ? valueOf(source.getClass()) : null);
    }

    /**
     * The type of the backing class, method parameter, field, or property described by this TypeDescriptor.
     * <p>Returns primitive types as-is.
     * <p>See {@link #getObjectType()} for a variation of this operation that resolves primitive types
     * to their corresponding Object types if necessary.
     *
     * @return the type, or {@code null}
     * @see #getObjectType()
     */
    public Class<?> getType() {
        return this.type;
    }

    /**
     * Variation of {@link #getType()} that accounts for a primitive type by returning its object wrapper type.
     * <p>This is useful for conversion service implementations that wish to normalize to object-based types
     * and not work with primitive types directly.
     */
    public Class<?> getObjectType() {
        return ClassUtils.resolvePrimitiveIfNecessary(getType());
    }

    /**
     * Narrows this {@link TypeDescriptor} by setting its type to the class of the provided value.
     * <p>If the value is {@code null}, no narrowing is performed and this TypeDescriptor is returned unchanged.
     * <p>Designed to be called by binding frameworks when they read property, field, or method return values.
     * Allows such frameworks to narrow a TypeDescriptor built from a declared property, field, or method return value type.
     * For example, a field declared as {@code java.lang.Object} would be narrowed to {@code java.util.HashMap}
     * if it was set to a {@code java.util.HashMap} value. The narrowed TypeDescriptor can then be used to convert
     * the HashMap to some other type. Annotation and nested type context is preserved by the narrowed copy.
     *
     * @param value the value to use for narrowing this type descriptor
     * @return this TypeDescriptor narrowed (returns a copy with its type updated to the class of the provided value)
     */
    public TypeDescriptor narrow(Object value) {
        if (value == null) {
            return this;
        }
        return new TypeDescriptor(value.getClass(), this.elementTypeDescriptor,
                this.mapKeyTypeDescriptor, this.mapValueTypeDescriptor, this.annotations);
    }

    /**
     * Cast this {@link TypeDescriptor} to a superclass or implemented interface
     * preserving annotations and nested type context.
     *
     * @param superType the super type to cast to (can be {@code null}
     * @return a new TypeDescriptor for the up-cast type
     * @throws IllegalArgumentException if this type is not assignable to the super-type
     * @since 3.2
     */
    public TypeDescriptor upcast(Class<?> superType) {
        if (superType == null) {
            return null;
        }
        Assert.isAssignable(superType, getType());
        return new TypeDescriptor(superType, this.elementTypeDescriptor,
                this.mapKeyTypeDescriptor, this.mapValueTypeDescriptor, this.annotations);
    }

    /**
     * Returns the name of this type: the fully qualified class name.
     */
    public String getName() {
        return ClassUtils.getQualifiedName(getType());
    }

    /**
     * Is this type a primitive type?
     */
    public boolean isPrimitive() {
        return getType().isPrimitive();
    }

    /**
     * The annotations associated with this type descriptor, if any.
     *
     * @return the annotations, or an empty array if none
     */
    public Annotation[] getAnnotations() {
        return this.annotations;
    }

    /**
     * Determine if this type descriptor has the specified annotation.
     *
     * @param annotationType the annotation type
     * @return <tt>true</tt> if the annotation is present
     */
    public boolean hasAnnotation(Class<? extends Annotation> annotationType) {
        return getAnnotation(annotationType) != null;
    }

    /**
     * Obtain the annotation associated with this type descriptor of the specified type.
     *
     * @param annotationType the annotation type
     * @return the annotation, or {@code null} if no such annotation exists on this type descriptor
     */
    @SuppressWarnings("unchecked")
    public <T extends Annotation> T getAnnotation(Class<T> annotationType) {
        for (Annotation annotation : this.annotations) {
            if (annotation.annotationType().equals(annotationType)) {
                return (T) annotation;
            }
        }
        for (Annotation metaAnn : this.annotations) {
            T ann = metaAnn.annotationType().getAnnotation(annotationType);
            if (ann != null) {
                return ann;
            }
        }
        return null;
    }

    /**
     * Returns true if an object of this type descriptor can be assigned to the location described by the given type descriptor.
     * <p>For example, valueOf(String.class).isAssignableTo(valueOf(CharSequence.class)) returns true because a String value can be assigned to a CharSequence variable.
     * On the other hand, valueOf(Number.class).isAssignableTo(valueOf(Integer.class)) returns false because, while all Integers are Numbers, not all Numbers are Integers.
     * <p>
     * For arrays, collections, and maps, element and key/value types are checked if declared.
     * For example, a List&lt;String&gt; field value is assignable to a Collection&lt;CharSequence&gt; field, but List&lt;Number&gt; is not assignable to List&lt;Integer&gt;.
     *
     * @return true if this type is assignable to the type represented by the provided type descriptor
     * @see #getObjectType()
     */
    public boolean isAssignableTo(TypeDescriptor typeDescriptor) {
        boolean typesAssignable = typeDescriptor.getObjectType().isAssignableFrom(getObjectType());
        if (!typesAssignable) {
            return false;
        }
        if (isArray() && typeDescriptor.isArray()) {
            return getElementTypeDescriptor().isAssignableTo(typeDescriptor.getElementTypeDescriptor());
        } else if (isCollection() && typeDescriptor.isCollection()) {
            return isNestedAssignable(getElementTypeDescriptor(), typeDescriptor.getElementTypeDescriptor());
        } else if (isMap() && typeDescriptor.isMap()) {
            return isNestedAssignable(getMapKeyTypeDescriptor(), typeDescriptor.getMapKeyTypeDescriptor()) &&
                    isNestedAssignable(getMapValueTypeDescriptor(), typeDescriptor.getMapValueTypeDescriptor());
        } else {
            return true;
        }
    }

    // indexable type descriptor operations

    /**
     * Is this type a {@link Collection} type?
     */
    public boolean isCollection() {
        return Collection.class.isAssignableFrom(getType());
    }

    /**
     * Is this type an array type?
     */
    public boolean isArray() {
        return getType().isArray();
    }

    /**
     * If this type is an array, returns the array's component type.
     * If this type is a {@link Collection} and it is parameterized, returns the Collection's element type.
     * If the Collection is not parameterized, returns null indicating the element type is not declared.
     *
     * @return the array component type or Collection element type, or {@code null} if this type is a Collection but its element type is not parameterized
     * @throws IllegalStateException if this type is not a java.util.Collection or Array type
     */
    public TypeDescriptor getElementTypeDescriptor() {
        assertCollectionOrArray();
        return this.elementTypeDescriptor;
    }

    /**
     * If this type is a {@link Collection} or an Array, creates a element TypeDescriptor from the provided collection or array element.
     * <p>Narrows the {@link #getElementTypeDescriptor() elementType} property to the class of the provided collection or array element.
     * For example, if this describes a java.util.List&lt;java.lang.Number&lt; and the element argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer.
     * If this describes a java.util.List&lt;?&gt; and the element argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer as well.
     * <p>Annotation and nested type context will be preserved in the narrowed TypeDescriptor that is returned.
     *
     * @param element the collection or array element
     * @return a element type descriptor, narrowed to the type of the provided element
     * @throws IllegalStateException if this type is not a java.util.Collection or Array type
     * @see #narrow(Object)
     */
    public TypeDescriptor elementTypeDescriptor(Object element) {
        return narrow(element, getElementTypeDescriptor());
    }

    // map type descriptor operations

    /**
     * Is this type a {@link Map} type?
     */
    public boolean isMap() {
        return Map.class.isAssignableFrom(getType());
    }

    /**
     * If this type is a {@link Map} and its key type is parameterized, returns the map's key type.
     * If the Map's key type is not parameterized, returns null indicating the key type is not declared.
     *
     * @return the Map key type, or {@code null} if this type is a Map but its key type is not parameterized
     * @throws IllegalStateException if this type is not a java.util.Map
     */
    public TypeDescriptor getMapKeyTypeDescriptor() {
        assertMap();
        return this.mapKeyTypeDescriptor;
    }

    /**
     * If this type is a {@link Map}, creates a mapKey {@link TypeDescriptor} from the provided map key.
     * <p>Narrows the {@link #getMapKeyTypeDescriptor() mapKeyType} property to the class of the provided map key.
     * For example, if this describes a java.util.Map&lt;java.lang.Number, java.lang.String&lt; and the key argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer.
     * <p>If this describes a java.util.Map&lt;?, ?&gt; and the key argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer as well.
     * <p>Annotation and nested type context will be preserved in the narrowed TypeDescriptor that is returned.
     *
     * @param mapKey the map key
     * @return the map key type descriptor
     * @throws IllegalStateException if this type is not a java.util.Map
     * @see #narrow(Object)
     */
    public TypeDescriptor getMapKeyTypeDescriptor(Object mapKey) {
        return narrow(mapKey, getMapKeyTypeDescriptor());
    }

    /**
     * If this type is a {@link Map} and its value type is parameterized, returns the map's value type.
     * <p>If the Map's value type is not parameterized, returns null indicating the value type is not declared.
     *
     * @return the Map value type, or {@code null} if this type is a Map but its value type is not parameterized
     * @throws IllegalStateException if this type is not a java.util.Map
     */
    public TypeDescriptor getMapValueTypeDescriptor() {
        assertMap();
        return this.mapValueTypeDescriptor;
    }

    /**
     * If this type is a {@link Map}, creates a mapValue {@link TypeDescriptor} from the provided map value.
     * <p>Narrows the {@link #getMapValueTypeDescriptor() mapValueType} property to the class of the provided map value.
     * For example, if this describes a java.util.Map&lt;java.lang.String, java.lang.Number&lt; and the value argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer.
     * If this describes a java.util.Map&lt;?, ?&gt; and the value argument is a java.lang.Integer, the returned TypeDescriptor will be java.lang.Integer as well.
     * <p>Annotation and nested type context will be preserved in the narrowed TypeDescriptor that is returned.
     *
     * @param mapValue the map value
     * @return the map value type descriptor
     * @throws IllegalStateException if this type is not a java.util.Map
     */
    public TypeDescriptor getMapValueTypeDescriptor(Object mapValue) {
        return narrow(mapValue, getMapValueTypeDescriptor());
    }


    // deprecations in Spring 3.1

    /**
     * Returns the value of {@link TypeDescriptor#getType() getType()} for the {@link #getElementTypeDescriptor() elementTypeDescriptor}.
     *
     * @throws IllegalStateException if this type is not a java.util.Collection or Array type
     * @deprecated in Spring 3.1 in favor of {@link #getElementTypeDescriptor()}
     */
    @Deprecated
    public Class<?> getElementType() {
        return getElementTypeDescriptor().getType();
    }

    /**
     * Returns the value of {@link TypeDescriptor#getType() getType()} for the {@link #getMapKeyTypeDescriptor() getMapKeyTypeDescriptor}.
     *
     * @throws IllegalStateException if this type is not a java.util.Map
     * @deprecated in Spring 3.1 in favor of {@link #getMapKeyTypeDescriptor()}
     */
    @Deprecated
    public Class<?> getMapKeyType() {
        return getMapKeyTypeDescriptor().getType();
    }

    /**
     * Returns the value of {@link TypeDescriptor#getType() getType()} for the {@link #getMapValueTypeDescriptor() getMapValueTypeDescriptor}.
     *
     * @throws IllegalStateException if this type is not a java.util.Map
     * @deprecated in Spring 3.1 in favor of {@link #getMapValueTypeDescriptor()}
     */
    @Deprecated
    public Class<?> getMapValueType() {
        return getMapValueTypeDescriptor().getType();
    }

    // package private helpers

    TypeDescriptor(AbstractDescriptor descriptor) {
        this.type = descriptor.getType();
        this.elementTypeDescriptor = descriptor.getElementTypeDescriptor();
        this.mapKeyTypeDescriptor = descriptor.getMapKeyTypeDescriptor();
        this.mapValueTypeDescriptor = descriptor.getMapValueTypeDescriptor();
        this.annotations = descriptor.getAnnotations();
    }

    static Annotation[] nullSafeAnnotations(Annotation[] annotations) {
        return annotations != null ? annotations : EMPTY_ANNOTATION_ARRAY;
    }


    // internal constructors

    private TypeDescriptor(Class<?> type) {
        this(new ClassDescriptor(type));
    }

    private TypeDescriptor(Class<?> collectionType, TypeDescriptor elementTypeDescriptor) {
        this(collectionType, elementTypeDescriptor, null, null, EMPTY_ANNOTATION_ARRAY);
    }

    private TypeDescriptor(Class<?> mapType, TypeDescriptor keyTypeDescriptor, TypeDescriptor valueTypeDescriptor) {
        this(mapType, null, keyTypeDescriptor, valueTypeDescriptor, EMPTY_ANNOTATION_ARRAY);
    }

    private TypeDescriptor(Class<?> type, TypeDescriptor elementTypeDescriptor, TypeDescriptor mapKeyTypeDescriptor,
                           TypeDescriptor mapValueTypeDescriptor, Annotation[] annotations) {

        this.type = type;
        this.elementTypeDescriptor = elementTypeDescriptor;
        this.mapKeyTypeDescriptor = mapKeyTypeDescriptor;
        this.mapValueTypeDescriptor = mapValueTypeDescriptor;
        this.annotations = annotations;
    }

    private static TypeDescriptor nested(AbstractDescriptor descriptor, int nestingLevel) {
        for (int i = 0; i < nestingLevel; i++) {
            descriptor = descriptor.nested();
            if (descriptor == null) {
                return null;
            }
        }
        return new TypeDescriptor(descriptor);
    }


    // internal helpers

    private void assertCollectionOrArray() {
        if (!isCollection() && !isArray()) {
            throw new IllegalStateException("Not a java.util.Collection or Array");
        }
    }

    private void assertMap() {
        if (!isMap()) {
            throw new IllegalStateException("Not a java.util.Map");
        }
    }

    private TypeDescriptor narrow(Object value, TypeDescriptor typeDescriptor) {
        if (typeDescriptor != null) {
            return typeDescriptor.narrow(value);
        } else {
            return (value != null ? new TypeDescriptor(value.getClass(), null, null, null, this.annotations) : null);
        }
    }

    private boolean isNestedAssignable(TypeDescriptor nestedTypeDescriptor, TypeDescriptor otherNestedTypeDescriptor) {
        if (nestedTypeDescriptor == null || otherNestedTypeDescriptor == null) {
            return true;
        }
        return nestedTypeDescriptor.isAssignableTo(otherNestedTypeDescriptor);
    }

    private String wildcard(TypeDescriptor typeDescriptor) {
        return (typeDescriptor != null ? typeDescriptor.toString() : "?");
    }


    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof TypeDescriptor)) {
            return false;
        }
        TypeDescriptor other = (TypeDescriptor) obj;
        if (!ObjectUtils.nullSafeEquals(this.type, other.type)) {
            return false;
        }
        if (this.annotations.length != other.annotations.length) {
            return false;
        }
        for (Annotation ann : this.annotations) {
            if (other.getAnnotation(ann.annotationType()) == null) {
                return false;
            }
        }
        if (isCollection() || isArray()) {
            return ObjectUtils.nullSafeEquals(this.elementTypeDescriptor, other.elementTypeDescriptor);
        } else if (isMap()) {
            return ObjectUtils.nullSafeEquals(this.mapKeyTypeDescriptor, other.mapKeyTypeDescriptor) &&
                    ObjectUtils.nullSafeEquals(this.mapValueTypeDescriptor, other.mapValueTypeDescriptor);
        } else {
            return true;
        }
    }

    public int hashCode() {
        return getType().hashCode();
    }

    public String toString() {
        StringBuilder builder = new StringBuilder();
        for (Annotation ann : this.annotations) {
            builder.append("@").append(ann.annotationType().getName()).append(' ');
        }
        builder.append(ClassUtils.getQualifiedName(getType()));
        if (isMap()) {
            builder.append("<").append(wildcard(this.mapKeyTypeDescriptor));
            builder.append(", ").append(wildcard(this.mapValueTypeDescriptor)).append(">");
        } else if (isCollection()) {
            builder.append("<").append(wildcard(this.elementTypeDescriptor)).append(">");
        }
        return builder.toString();
    }

}
